The overall objective of this project is to identify and characterize important antigens in the Marek's disease herpesvirus (MDHV) system and to determine immunological relationships that exist especially as related to tumor formation and its prevention through a successful vaccine. One specific aim is to further purify, characterize and compare the soluble common extracellular A antigen (MDHV-A), intracellular B antigen (MDHV-B) and possible other antigens produced by cells infected either with MDHV or the vaccine virus, herpesvirus of turkeys (HVT), and to prepare high titered monospecific antisera against them. Previous work with the MDHV-A and B led to their identification as glycoproteins and their 200-fold purification with 25% recovery. Purified antigens and their monospecific antisera will be used to determine their relationship, if any, to each other, virion structural proteins, neutralizing antibody, interferon, and delayed hypersensitivity in infected birds. Plasma membranes from productively infected cells will be radiolabeled, purified, solubilized with detergents and analyzed by immune methods and SDS-PAGE for virus-specific proteins and antigens in order to determine the nature of membrane antigen (MA) which is currently defined by immunofluorescence. Special emphasis will be placed on possible relationships between soluble MDHV-A and MDHV-B or other antigens and the MA or other membrane associated antigens. Plasma membranes from a lymphoblastoid cell line will be analyzed in a similar manner to determine the nature of the Marek's associated tumor surface antigen (MATSA) which is also defined by immunofluorescence and is unrelated to the antigens described above. Radioiodination, immune co-precipitation and SDS-PAGE analysis are being used to identify MATSA. Plasma membranes from both types of cells, their solubilized components, and soluble counterparts will be purified and assayed for their ability to immunize and protect chickens against Marek's disease to determine the relative importance of virus-specific and tumor cell-specific antigens in protection.